SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/scuba-octopus-alternate-air-source

What is the spare second stage on your regulator, the alternate air source, for?

Sharing air with an out-of-air buddy.

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  1. Filling your BCD
  2. Checking tank pressure
  3. Sharing air with an out-of-air buddy ✔

Why: The octopus is an extra second stage, often bright yellow, so a buddy can breathe from your tank in an air emergency.

Huh, didn't know that: Sometimes the alternate second stage is built into the BCD inflator.

The dad joke
Why did the octopus share his air? He was an arms-length buddy.
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References

Answer: Sharing air with an out-of-air buddy. The octopus is an extra second stage, often bright yellow, so a buddy can breathe from your tank in an air emergency.

  1. PADI Gear: Regulators www.padi.com/gear/regulators
    Spare mouthpiece that provides an easy way to share air in case you need to help another diver.
    Checked 2026-10-12.
  2. PADI Gear: Regulators www.padi.com/gear/regulators
    Sometimes the alternate second stage is built into the inflator on your buoyancy control device (BCD).
    Checked 2026-10-12.

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